releases/2.6.32.12/0005-KVM-VMX-Save-restore-rflags.vm-correctly-in-real-mod.patch

   1 From 8a618f6f19f9bc88e8b5d75cbfbfedcb416246f3 Mon Sep 17 00:00:00 2001
   2 From: Avi Kivity <avi@redhat.com>
   3 Date: Thu, 8 Apr 2010 18:19:35 +0300
   4 Subject: KVM: VMX: Save/restore rflags.vm correctly in real mode
   5
   6 From: Avi Kivity <avi@redhat.com>
   7
   8 (Cherry-picked from commit 78ac8b47c566dd6177a3b9b291b756ccb70670b7)
   9
  10 Currently we set eflags.vm unconditionally when entering real mode emulation
  11 through virtual-8086 mode, and clear it unconditionally when we enter protected
  12 mode.  The means that the following sequence
  13
  14   KVM_SET_REGS  (rflags.vm=1)
  15   KVM_SET_SREGS (cr0.pe=1)
  16
  17 Ends up with rflags.vm clear due to KVM_SET_SREGS triggering enter_pmode().
  18
  19 Fix by shadowing rflags.vm (and rflags.iopl) correctly while in real mode:
  20 reads and writes to those bits access a shadow register instead of the actual
  21 register.
  22
  23 Signed-off-by: Avi Kivity <avi@redhat.com>
  24 Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
  26
  27 ---
  28  arch/x86/kvm/vmx.c |   24 +++++++++++++++---------
  29  1 file changed, 15 insertions(+), 9 deletions(-)
  30
  31 --- a/arch/x86/kvm/vmx.c
  32 +++ b/arch/x86/kvm/vmx.c
  33 @@ -61,6 +61,8 @@ module_param_named(unrestricted_guest,
  34  static int __read_mostly emulate_invalid_guest_state = 0;
  35  module_param(emulate_invalid_guest_state, bool, S_IRUGO);
  36
  37 +#define RMODE_GUEST_OWNED_EFLAGS_BITS (~(X86_EFLAGS_IOPL | X86_EFLAGS_VM))
  38 +
  39  struct vmcs {
  40         u32 revision_id;
  41         u32 abort;
  42 @@ -92,7 +94,7 @@ struct vcpu_vmx {
  43         } host_state;
  44         struct {
  45                 int vm86_active;
  46 -               u8 save_iopl;
  47 +               ulong save_rflags;
  48                 struct kvm_save_segment {
  49                         u16 selector;
  50                         unsigned long base;
  51 @@ -783,18 +785,23 @@ static void vmx_fpu_deactivate(struct kv
  52
  53  static unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
  54  {
  55 -       unsigned long rflags;
  56 +       unsigned long rflags, save_rflags;
  57
  58         rflags = vmcs_readl(GUEST_RFLAGS);
  59 -       if (to_vmx(vcpu)->rmode.vm86_active)
  60 -               rflags &= ~(unsigned long)(X86_EFLAGS_IOPL | X86_EFLAGS_VM);
  61 +       if (to_vmx(vcpu)->rmode.vm86_active) {
  62 +               rflags &= RMODE_GUEST_OWNED_EFLAGS_BITS;
  63 +               save_rflags = to_vmx(vcpu)->rmode.save_rflags;
  64 +               rflags |= save_rflags & ~RMODE_GUEST_OWNED_EFLAGS_BITS;
  65 +       }
  66         return rflags;
  67  }
  68
  69  static void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
  70  {
  71 -       if (to_vmx(vcpu)->rmode.vm86_active)
  72 +       if (to_vmx(vcpu)->rmode.vm86_active) {
  73 +               to_vmx(vcpu)->rmode.save_rflags = rflags;
  74                 rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM;
  75 +       }
  76         vmcs_writel(GUEST_RFLAGS, rflags);
  77  }
  78
  79 @@ -1431,8 +1438,8 @@ static void enter_pmode(struct kvm_vcpu
  80         vmcs_write32(GUEST_TR_AR_BYTES, vmx->rmode.tr.ar);
  81
  82         flags = vmcs_readl(GUEST_RFLAGS);
  83 -       flags &= ~(X86_EFLAGS_IOPL | X86_EFLAGS_VM);
  84 -       flags |= (vmx->rmode.save_iopl << IOPL_SHIFT);
  85 +       flags &= RMODE_GUEST_OWNED_EFLAGS_BITS;
  86 +       flags |= vmx->rmode.save_rflags & ~RMODE_GUEST_OWNED_EFLAGS_BITS;
  87         vmcs_writel(GUEST_RFLAGS, flags);
  88
  89         vmcs_writel(GUEST_CR4, (vmcs_readl(GUEST_CR4) & ~X86_CR4_VME) |
  90 @@ -1501,8 +1508,7 @@ static void enter_rmode(struct kvm_vcpu
  91         vmcs_write32(GUEST_TR_AR_BYTES, 0x008b);
  92
  93         flags = vmcs_readl(GUEST_RFLAGS);
  94 -       vmx->rmode.save_iopl
  95 -               = (flags & X86_EFLAGS_IOPL) >> IOPL_SHIFT;
  96 +       vmx->rmode.save_rflags = flags;
  97
  98         flags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM;
  99